The petrochemical and refining industries generally employ various processes where temperature must be measured reliably and with a high degree of accuracy. Typically, the environments in which temperature is measured require subjecting the temperature sensing devices to extreme conditions, including radiant and direct thermal energy sources with temperatures in excess of 1300° F. These harsh conditions present challenges with respect to reliably providing accurate temperature measurements of a particular structure over extended periods of time. For instance, it is oftentimes desirable to acquire temperature measurements of various structures, such as the surface (or skin) of tubes or other conduits, that are present within a furnace or other high temperature vessel used in a refining process to ensure both that the structure is not overheating and that the process is occurring at a desired temperature. However, the high radiant energy within the furnace can make it difficult to obtain an accurate measurement of the surface of a particular structure within the furnace since the temperature measurement device is exposed to thermal sources other than the measured surface. In addition to the harsh radiant conditions, the temperature sensing device also may be exposed to the open flames of the furnace, which can have a detrimental effect on the longevity of the temperature sensing device. As a result, the temperature sensing device often is replaced multiple times over the life of the vessel, which requires shutdown of the refining process. Consequently, if a failed instrumentation cannot be readily removed and a replacement readily installed, the processing downtime can be extremely costly.
Known temperature sensing devices that are used in refining processes include an extractable thermocouple device where the sheath is blindly fed into position through a guide that is welded to the surface of a furnace tube. However, this device is difficult to reliably position both in a desired location and so that the device makes adequate thermal contact with the tube surface at the desired location. For another known temperature sensing device, the thermocouple sheath is welded to a mounting pad that, in turn, is welded directly to the surface of the furnace tube. Removal and replacement of this type of device is difficult due to the time-consuming steps needed to prepare the surface of the tube so that the replacement device can be attached. Such preparation steps may include grinding the tube surface at the location of attachment to remove substances that may impede adherence of the temperature sensor and extensive heat treating of the tube so that the device can be welded thereto. These preparation processes can be very costly in terms of labor and processing downtime. In addition, grinding and heat treating of the tube surface ultimately will result in the need to replace the tube, which likewise is an extremely expensive process.